1. Field of Invention
The present invention relates to a bi-direction driver IC and a method for bi-directionally driving an object, such as for controlling a motor to rotate in two directions.
2. Description of Related Art
In certain applications, an object such as a motor needs to rotate bi-directionally, for controlling, e.g., a rear mirror of a vehicle. Referring to FIG. 1, a prior art bi-direction motor driver IC module requires at least three wires. In order to control the forward and backward rotations of the motor M, the IC module is provided with three pins, including two power pins and one control pin, wherein the positive power pin is connected to a positive voltage and the negative power pin is connected to ground (or a negative voltage); the third control pin CTL receives an external input signal which controls the rotation direction of the motor. In this prior art, the two power pins can not be interchanged; the positive power pin must be connected to the positive voltage, and the negative power pin must be connected to ground (or the negative voltage). However, in certain applications, the system only provides two AC power connections, such as in the control system for rear mirror of a vehicle. Presently, the majority of vehicles only provide two AC power connections. In this case, the three pin module can not function, because there is no control signal, and the three pin module can not cooperate with the AC power connections.
The current through an IC has to flow from its power supply to ground; the power pins thereof can not be reversely connected. If they are reversely connected, the IC can not operate and may be damaged. Because of the above reason, there has not been any bi-direction motor driver IC with only two pins in the past. Conventionally in the control system for vehicle rear mirror or other similar control systems, if it is required to operate in cooperation with two AC power connections, the control circuit is formed by multiple discrete devices. Yet, these discrete devices can not be integrated into a general IC.
In view of the disadvantages of the foregoing prior art, the present invention provides a bi-direction driver IC with two power pins, to be coupled to an AC power supply supplying alternating positive and negative voltages. The bi-direction driver IC can switch the direction of its output current, and hence it can be used for (but not limited to) driving a motor which requires to rotate in two directions. In addition, the present invention also provides a method for bi-directionally driving an object (for example but not limited to a motor).